This invention relates to pressure regulating devices, and more particularly, it relates to an improved control valve for metering fluid flow in response to a control fluid pressure signal.
Metering valves provide adjustment of fluid flow between a source of higher fluid pressure and a volume of lower pressure fluid. Accurate fluid flow control requires that the metering member not oscillate in turbulent flow, because oscillation causes the fluid flow to become unstable. Furthermore, a metering valve must be able to completely close the fluid flow path, shutting off fluid flow. A precise fit is required between metering members and the borehole to ensure a proper closing seal and no oscillation. In prior art valves, fluid flow metering is achieved by use of a tapered plunger or ball which is moved within a borehole in the fluid flow path. Such valves typically do not have the precise fit between the metering member and borehole required for good fluid flow metering. Because of tolerance build-up a certain looseness of mating parts is required for the parts to be self-aligning so as to completely close. This looseness permits movement of the parts and though not intended, movement due to the turbulence of flowing fluid medium. This movement of the control element imparts an oscillating characteristic to the flow and pressure of the fluid.